Really depends on the niche. I have a new client I'm beginning to manage at one of the agencies I work at and she's in a niche within real estate. So not real estate but a very specific sub category. It's a small niche, where she's teaching this topic. She's been at it for 15 years now, hundreds of videos and frankly there's just not enough topic to make a channel around. Really stretching it, there may be a video a month there, BUT I recommended to her that she's starts focusing on ad production with a series of 12 actual videos a year or one a month, so people can see her authority on the subject when they visit her channel. Kind of like Charlie Morgan if you've ever seen his stuff. As a teaching concept it's very valuable to people, but as a YouTube niche, it cannot consistently produce good content, hence putting a focus on customers and not viewers. So, my biggest piece of advice would be to look at their niche. Is it too small, is it TOO niche, we always hear about niching down but that can go too far sometimes, is it viable at all? Sometimes we try to Sudoku a bunch of broken parts together, but it may be easier starting over than fixing every individual part of a channel. Additionally, having a massive amount of failed videos, just from a viewer perspective, looks like the creator doesn't really know what they're doing or they don't have authority to speak on the subject. While it's true that some channels can do 180s it really depends on the niche. Is it gaming? Sure, no one cares about a huge back catalogue, but if it's anything having to do with knowledge, teaching or authority, I would start over or hide all of those failed videos at the very least to maintain strong footing with the audience.